// v-dialogDrag: 弹窗拖拽属性
import Vue from 'vue';
Vue.directive('dialogDrag', {
    bind(el, binding, vnode, oldVnode) {
      const dialogHeaderEl = el.querySelector('.el-dialog__header');
      const dragDom = el.querySelector('.el-dialog');
      //dialogHeaderEl.style.cursor = 'move';
      dialogHeaderEl.style.cssText += ';cursor:move;'
      dragDom.style.cssText += ';top:0px;'
    
      // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);
      const sty = (function() {
          if (window.document.currentStyle) {
              return (dom, attr) => dom.currentStyle[attr];
          } else{
              return (dom, attr) => getComputedStyle(dom, false)[attr];
          }
      })()    
       
      dialogHeaderEl.onmousedown = (e) => {
        // 鼠标按下，计算当前元素距离可视区的距离
        const disX = e.clientX - dialogHeaderEl.offsetLeft;
        const disY = e.clientY - dialogHeaderEl.offsetTop;
         
        const screenWidth = document.body.clientWidth; // body当前宽度
          const screenHeight = document.documentElement.clientHeight; // 可见区域高度(应为body高度，可某些环境下无法获取) 
           
          const dragDomWidth = dragDom.offsetWidth; // 对话框宽度
          const dragDomheight = dragDom.offsetHeight; // 对话框高度
           
          const minDragDomLeft = dragDom.offsetLeft;
          const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth;
           
          const minDragDomTop = dragDom.offsetTop;
          const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight;
    
         
        // 获取到的值带px 正则匹配替换
        let styL = sty(dragDom, 'left');
        let styT = sty(dragDom, 'top');
    
        // 注意在ie中 第一次获取到的值为组件自带50% 移动之后赋值为px
        if(styL.includes('%')) {
          styL = +document.body.clientWidth * (+styL.replace(/\%/g, '') / 100);
          styT = +document.body.clientHeight * (+styT.replace(/\%/g, '') / 100);
        }else {
          styL = +styL.replace(/\px/g, '');
          styT = +styT.replace(/\px/g, '');
        };
         
        document.onmousemove = function (e) {
          // 通过事件委托，计算移动的距离 
                  let left = e.clientX - disX;
                  let top = e.clientY - disY;
                   
                  // 边界处理
                  if (-(left) > minDragDomLeft) {
                      left = -(minDragDomLeft);
                  } else if (left > maxDragDomLeft) {
                      left = maxDragDomLeft;
                  }
                   
                  if (-(top) > minDragDomTop) {
                      top = -(minDragDomTop);
                  } else if (top > maxDragDomTop) {
                      top = maxDragDomTop;
                  }
    
          // 移动当前元素 
                  dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;
        };
    
        document.onmouseup = function (e) {
          document.onmousemove = null;
          document.onmouseup = null;
        };
      } 
    }
  })